Relevant fastenings in which a fastening screw is arranged telescopically in a sleeve, wherein a knurling of the screw shank at a distance from the screw head in cooperation with a necking at the upper end of the sleeve to ensure retention of the fastening screw and sleeve, are already known.
In one embodiment, a head flange of the sleeve is supported on a rubber ring which is pressed into a receiver of a cylinder head cover. A foot flange of the sleeve is buttoned into a through-bore with an undercut of a further rubber part which is arranged between the cylinder head cover and the cylinder head. By way of this a decoupling is effected, i.e. the hard screw head as well as the sleeve are not pressed directly against the cover which may consist of plastic. On the other hand the sleeve of metal prevents excess pressing of the rubber parts. With this arrangement, a secure temporary assembly of the screw, sleeve and rubber parts to the cylinder head cover is possible which permits transport in any position up to assembly on the cylinder head. It is, however of a disadvantage that the screw, when mounting the cylinder head cover, with its lower end may slide over the sealing surfaces of the cylinder head and cause damage. With long screws the knurling may even press against the necking of the sleeve and loosen the temporary assembly. With another fastening, a rubber ring is arranged between the head flange of the sleeve and the assembly part. The rubber ring below has a collar with three hooks distributed on the circumference which engage behind the undercuts in a through-bore of the assembly part. The collar however must have a certain thickness so that on pressing into the through-bore they are not pressed axially together. Because the hooks form the only securement this fastening is not adequately safe in transport. Furthermore the telescoping ability is limited by the abutment of the knurling on the necking so that there prevails a relatively long screwing out of the sleeve and thus the guiding as well as the assembly of the cylinder head cover (assembly part) is made more difficult.
With another fastening the rubber ring is pressed into the assembly part at its large circumference. This sleeve may be arranged in the rubber ring with play so that it may be telescoped up to the abutment of its foot flange on a collar of the rubber ring. Since the screw may also be displaced with respect to the sleeve there results as a whole an enlarged ability to telescope which favours the application on a carrier component. However the circumferential pressing does not ensure any particularly secure preassembly in the assembly part.
With yet another fastening, the foot flange engages behind several undercuts, which in a cover part are preferably injected from plastic. The manufacture requires complicated injection tools. Furthermore the undercuts on pressing in the foot flange may shear off so that the transport securement is not ensured.
It is an object of the invention to provide a fastening of an assembly part to a carrier part, which improves the security of a temporary pre-assembly, favours an assembly without the protrusion of the screw ends out of the assembly part and may be applied in the case of decoupling as well as in the hard screw case.